The present invention relates to a damper disc assembly suitable for a friction clutch disc for an automobile, and more particularily to a disc assembly in which a sub-plate is employed to attain stepped damping characteristics.
In the U.S. patent application Ser. No. 347,157, the applicant of the invention has already disclosed a disc as illustrated in FIG. 1. In FIG. 1, a spline hub 1 is provided with a radial flange 2 divided into a radially inner portion 3 and an outer portion 4. According to this structure, the outer portion 4 is designed to turn with respect to the inner portion 3 so as to increase damping effect or absorbing effect for torque vibration.
However, this disc has following disadvantages. Since the inner and outer portions 3 and 4 are required to have integral projections 5 and 6 as well as recesses 7 and 8 for engaging with each other, it is difficult to form and machine the flange 2. Especially, the inner portion 3 is formed integrally with the hub 1 and requires small protrusions 9 on the inner surfaces of the recesses for holding springs, which make the manufacturing extremely difficult. Further, a damping characteristic in first step (in small torsion angle area) may become unstable, and it may be difficult to obtain sufficient strength.
Accordingly, it is an object of the invention to provide an improved damper disc assembly, overcoming the above noted disadvantages.
The essence of the invention is to provide a damper disc assembly in which a pair of annular flanges are disposed at both sides of a sub-plate unrotatably connected to a hub.
Other and further objects, features and advantages of the invention will appear more fully from the following description of the preferred embodiments of the invention.